Accretion definition, an increase by natural growth or by gradual external addition; growth in size or extent. See more.
Alveoli are tiny sacs within our lungs that allow oxygen and carbon dioxide to move between the lungs and bloodstream. Learn more about how they function and quiz your knowledge at the end.
Its structure is that of a balloon, and that helps it function during inhalation because it opens up to allow air to make contact with a large area to perform gas exchange. The structure of the alveoli is that there are blood vessels wrapping around them. Then, oxygenin from the alveoli can enter the blood.